test-drb April 2009

test-drb@ccmp.vtda.org

204 participants
261 discussions

by bob＠theadamsons.co.uk

As an unexpected freebie while I was picking up another pdp8 I've acquired a small pdp11/15. I'm really an 8-man so this is a bit of a foreigner but it seemed a shame to let it be thrown away. It seems to be a fairly small system in a single box but beautifully clean for a change ;o). The configuration sheet shows KC11, KF11-A, DL11, KG11-A, MM11-F, MM11-f, DD11-A and H720F which seems to reflect the contents OK. I've started browsing around but I'd welcome anyone giving me a rundown on what these modules build up to. I was quite interested to see the construction method with the cards upside-down in the backplane and a snazzy rotatable rack mount for servicing - unusual (to me at least). Bob

15 years, 8 months

Anyone willing to read some Amstrad/Amsoft 3" floppies?

by sethm＠loomcom.com

Hi folks, My aunt just emailed me to let me know she's got a friend with some old floppies that she needs to get files off of. They're Amsoft CF2 3" floppies, unfortunately something I've never had in my collection, so I can't really help. If anyone on the list has easy access to an Amstrad or ZX Spectrum system with a CF2 drive and would be willing to help (possibly for a fee, I have no idea whether/what they'd be willing to pay), please contact me off list, and I'll try to get you connected! Thanks, -Seth

15 years, 8 months

Mystery Core

by mloewen＠cpumagic.scol.pa.us

Can anyone identify these boards? http://sturgeon.css.psu.edu/~mloewen/DSC01381.JPG http://sturgeon.css.psu.edu/~mloewen/DSC01382.JPG http://sturgeon.css.psu.edu/~mloewen/DSC01463.JPG They're stamped IBM, with etched numbers LBJ5360, LBJ5403 and LKJ12470. The owner says they were given to him in 1978, and were supposedly from North Bay, Ontario. Mike Loewen mloewen at cpumagic.scol.pa.us Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/

15 years, 8 months

altair 8800b style switches

by aek＠bitsavers.org

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250414411275 Looks like he has several lots. I'm pretty sure these are the ones used on the 8800B front panel.

15 years, 8 months

More Apple II fun - 4116's

by tshoppa＠wmata.com

Mike asks: > My real question is - 9 faulty out of 48, spread across both machines, > seems very high. Are 4116s that unreliable? Or perhaps they're quite > sensitive to power supply problems? It isn't unusual to find that many years after manufacture, that a particular batch of DRAM chips aren't reliable anymore. DEC and other memory board makers used to keep internal lists of known good batches and known bad batches of chips, and even kept track of what brand/batch are shipped with each memory board for long-term reliability tracking. But it seems more likely that something marginal in the timing of the motherboards or the power supply or something else is causing your observed flakiness. I don't really understand what you mean about the Apple II's "wouldn't boot", though. They do not do an extensive (or any!) power-on memory test but maybe loading DOS 3.3 is hitting RAM hard enough at power on that it's turning somethng else up. As others have noted, just going into BASIC at power-up doesn't hit memory too hard, and the quickie tests of going into hi-res graphics and looking for flakiness on the screen is useful if not definitive. Tim.

15 years, 8 months

DEC VT05 with OS/8 -- System handler?

by hachti＠hachti.de

Hi, I just try to get a VT05 working with my PDP-8/e. Having a tuned KL8E interface at 2400 baud. I need fill characters.... Found a KL8E.PA in the OS/8 V3D sources. It is a two page handler and works. But how do I get my system to use it as terminal handler? Or is there another one? Best wishes, Philipp :-) -- http://www.hachti.de

15 years, 8 months

More broken Apples...

by roger.holmes＠microspot.co.uk

First sorry for the delayed response. Back when the Apple ][ Europlus were being sold new, and when Microspot was actively selling them, one of my favourite ways of finding RAM problems, was to type HGR2<return> and watch the screen. It switched to displaying a large chunk of the second 16k bank as pure raster graphics and then sets it all to black (zero). It only displays seven bits of each byte on a mono monitor but any dead chips in those seven shows up as recurring white (or randomly flashing) vertical lines. If there is a fault in the first bank then the machine probably will not start up, but if it does, typing HGR<return> displays the first bank similarly but with four(?) lines of text at the bottom. You can switch the RAM around to test bank 3 and the eighth bit of each byte. By using the Basic commands (moveto and lineto?) you can find out which bit has failed, or by switching RAM chips. On 26 Apr 2009, at 18:00, cctalk-request at classiccmp.org wrote: > > Message: 3 > Date: Sun, 26 Apr 2009 23:38:28 +1200 > From: Mike van Bokhoven <mike at fenz.net> > Subject: More broken Apples... > To: General Discussion: On-Topic and Off-Topic Posts > <cctalk at classiccmp.org> > Message-ID: <49F447B4.1000708 at fenz.net> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Well, I dragged those Apple IIs out of storage, and spent this evening > poking at them, with some success. Thought I'd post my results here, > and > hope that someone has some suggestions for me. > > There are three machines in total; one an Apple II Europlus, the other > two generic II+ clones. > > The first thing I did was run them up - all dead, garbage on the > screen. > Same as last time I looked at them. Step 2 - pull all the cards and > try > again. After that, one of the clones ran up fine; turns out that the > 'language card' (16k memory expansion) was killing it. Good stuff - > one > running Apple II, even if it's not an original. > > Unfortunately, the other two weren't quite so cooperative. I decided > to > look at the other clone first, as its behaviour was pretty > interesting. > The screen was entirely full of apostrophes to begin with, but > randomly, > blocks of them would change to lower case 'p's, and back, flickering > very quickly. It responded to a reset by changing the pattern of ps, > though they tended to appear in the same place. I found the ASCII > values > interesting: > > ' = 0x60 = 0110 0000 > p = 0x70 = 0111 0000 > > So, on reset, perhaps it's clearing half the bits per byte, and the > other four have a problem. Reseting the machine tended to lead to > random > behaviour for a bit, such as random display changes, and speaker > clicks. > At one point, the display switched to high-res mode, and I could see > that a large amount of memory had the same sort of pattern through it, > and was flickering the same way text was; I guess the entire memory > space is like that. Perhaps bits 5 and 6 are permanently stuck. > > I checked the CPU's behaviour; on reset, the address and data lines > would run for at least a short time, so I'm guessing the CPU is likely > to be OK. Often they would continue to run, at which time I'd see the > flickering. Other times, activity would stop, and the flickering would > also stop, usually leaving a screen full of 's. > > So, my next step is to track down a schematic for the machine, and see > what I can figure out. I'm guessing I should look first at anything > that > deals with the high four bits of memory. Thoughts, suggestions and > intuitive guesses welcome!

15 years, 8 months

machine room in a trailer?

by technobug＠comcast.net

On Wed, 29 Apr 2009 15:33:43 -0600, Richard <legalize at xmission.com> wrote: > Reasonable idea. I've seen surplus environment controlled trailers > for sale on govliquidation. This is a great way of going if you are willing to re-rack your equipment. The electronics trailers are specially designed to channel cooling to the racks - some having zone controls. Generally, there is also sufficient power distribution to handle the equipment you described. A number of years ago I outfitted a thirty-foot surplus equipment trailer with a Modcomp II, data recorders, printer, and data acquisition equipment for an atmospheric optical transfer function experiment. The trailer I came up with had a row of racks that covered one side leaving the other for a console and printer and room for everyone involved to escape the elements. We operated out of Tucson, Arizona with sites at Cape Canaveral in the summer, Lake Tahoe in the winter, and Bolder, Colorado in the summer. About 10,000 miles of travel in all with no equipment failures! There were two zones of cooling: one for the equipment in the bays and the other for the personnel space. There was over 100 Amps available in the racks with 3-phase 220/110V wiring. Another avenue to investigate are surplus equipment shelters. These shelters have environmental systems, racks, and power distribution. You hire a crane/big fork lift and a flatbed to move the beasts and generally will go for less than the trailers. CRC

15 years, 8 months

Transistors...

by ajp166＠bellatlantic.net

> >Subject: Re: Transistors... > From: Fred Cisin <cisin at xenosoft.com> > Date: Wed, 29 Apr 2009 11:50:48 -0700 (PDT) > To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > >On Tue, 28 Apr 2009, Allison wrote: >> Common base transistor has current gain of .99999.. and voltage gain >1 as >> well as power gain. Wire is .9999999.. for all those. > >Is common wire really THAT close (.9999999..) to 1.0? >I always assumed that wire losses were more than that. >Or does that require superconductors? Not quite but compared to many other things unless second order effects are important it's practical to use 1. Mostly as what you put in is what out get out for small systems at low curents and moderatly low frequencies. At grid tranmission line currents and distances even that .000001 part is significant. At RF, noticable at VHF and higher then the resistivity of the surface is more important than bulk due to skin effect. Thats a whole nother can of worms. Allison

15 years, 8 months

free/pick-up: Origin 2000 sgi 2400, Tilburg, The Netherlands

by gyorpb＠gmail.com

On Apr 29, 2009, at 20:29, Joost van Baal wrote: > The machine will be rescued by the Centre for Computing History > (www.computinghistory.org.uk) near Cambridge, UK. (It might even > get hooked up > on the internet, within a couple of months.) Thanks locutus for > help in > mediating. See http://abramowitz.uvt.nl/sgi.txt for latest status. Joost asked me to communicate this to all of you, so here it is. .tsooJ

15 years, 8 months

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test-drb April 2009